Inflation systems for safety systems, such as evacuation slides and life rafts that are required to be carried on-board aircraft, generally use compressed gas for inflation. For example, the evacuation slide and/or life raft may be coupled with a container of compressed gas used to inflate the structure. One or multiple chambers of the safety system may inflated upon (or before) deployment of the safety system.
As background, an evacuation slide is an inflatable slide used to allow passengers and crew to evacuate an aircraft in the event of an emergency. An evacuation slide is required on all passenger-carrying aircraft where the door sill height cannot allow evacuation of persons from the door uninjured. The Federal Aviation Administration (FAA) requires slides on all aircraft doors where the floor is 6 feet (1.8 m) or more above the ground. Such slides are generally provided with one or more inflatable chambers.
Evacuation slides are packed and held within the door structure inside the slide/door bustle, which is a protruding part inside an aircraft door. A slide bustle typically houses the evacuation slide, as well as the inflation system that will be used to inflate the slide. Many but not all slides are also designed to double as life rafts in case of a water landing and evacuation.
It is desirable for evacuation slides and/or life rafts to inflate quickly and reliably. The FAA requires evacuation of the entire aircraft in 90 seconds using 50% of the available evacuation exits. To meet this requirement, evacuation slides should deploy in less than 10 seconds. For large, wide body aircraft such as A300s and B747s, this means a successful deployment should be complete in about 5-7 seconds (depending upon whether conditions, such as temperature and winds). A high pressure of gas is thus required to make this deployment happen in the desired time period.
In use, if the aircraft doors are opened while the slide bustle is in an armed state, opening of the door pulls the slide pack out of the slide bustle. Once freed, the slide will fall (under gravity), pulling a pin from a valve of a container containing compressed gas and causing the slide to inflate. Currently, evacuation slides and life rafts use non-explosive, inert gas inflation systems. Similar systems are also used for life rafts.
The inflation system usually includes a pressurized cylinder, a regulating valve, high pressure hoses, and aspirators. The cylinder can be from about 100 to about 1600 cubic inches and filled to about 3000 psig with either gaseous nitrogen, or a mixture of gaseous CO2 and nitrogen. In order to accommodate weight considerations, most cylinders are now made of aluminum or alloy cores wrapped with fiberglass, carbon fiber or other lightweight materials rather than steel, but weight reductions are still desirable. The regulating valve is used to mechanically meter out the gas at a desired rate.
However, inflation of the evacuation slides and life rafts using compressed gas can present various challenges. For example, compressed gas can be dangerous, difficult to transport, and prone to leaks. Compressed gas containers also carry an associated size and weight, which can be undesirable on board an aircraft where size and weight are at a premium. Use of compressed gas is also limited to a single use. Accordingly, improved inflation systems are desirable.